In an experimental model of thermal injury, what effect would administering an antihistamine prior to injury have on dye extravasation?

• A. Peak A only
• B. Peak B only
• C. Both Peak A and B
• D. Neither Peak A nor B

Answer: (A)

Administering an antihistamine prior to a thermal injury would likely lead to a reduction in the extravasation of dye that corresponds to the immediate vascular response associated with histamine release. In the context of thermal injuries, there are typically two phases of dye extravasation: an early phase (often referred to as Peak A) and a later phase (Peak B).

Histamine plays a critical role in the acute inflammatory response by causing vasodilation and increasing vascular permeability, which leads to the rapid extravasation of plasma proteins and other molecules into the tissue. By administering an antihistamine before the injury, you would inhibit the effects of histamine, thereby reducing the extent of the immediate response that occurs after the injury.

As a result, one would observe a significant effect on the early phase of dye extravasation (Peak A), which is predominantly mediated by the actions of histamine. However, the later phase (Peak B) is often influenced by other mediators of inflammation, such as cytokines and chemokines, which continue to promote extravasation even in the absence of histamine.

Therefore, the correct assertion is that the antihistamine would reduce extravasation associated with Peak A but would not have a